<!DOCTYPE HTML>
<html>
<body style="width: 600px; height: 400px;">
  <div style="position: absolute; left: 0px; top: 0px;
              width=600px height=600px">
    <div style="position: absolute; left: 0px; top: 0px;
                width: 600px; height: 400px;
                background-color: green;"></div>
    <div style="position: absolute; left: 300px; top: 400px;
                width: 100px; height: 100px;
                background-color: red;"></div>
    <div style="position: absolute; left: 0px; top: 500px;
                width: 600px; height: 100px;
                background-color: yellow;"></div>
  </div>
</body>
</html>
